//
//  Person.h
//  Objective-C
//
//  Created by S_Line on 2018/8/15.
//  Copyright © 2018年 S_Line. All rights reserved.
//

#import <Foundation/Foundation.h>

@class Father, Son;

@interface Person : NSObject

@end

@interface Father : Person

@property (nonatomic, strong) Son *son;

@end

@interface Son : Person

@property (nonatomic, strong) Father *father;

@end
